Although the first rail services will not be operational until 2017, a lot of construction work has been accomplished in the last five years, as seen in the before-and-after photo animations below.

When all is finished, Crossrail will make schlepping around London much faster and easier by reducing crowds on existing rail services, like the London Underground and National Rail. Europe's largest construction project of the moment comes at a cost of £14.8 billion pounds ($23 billion).

A total of eight tunnel boring machines have been working non-stop over the last two years to construct 42,000 metres of new tunnels beneath London.

Crossrail/Business Insider

Tunnel work at Royal Oak in west London began in 2012. By 2014, tunnel driving machines Phyllis and Ada each constructed 6,800 metres of tunnels between Royal Oak and Farringdon.

Crossrail/Business Insider

More than a century of built-up soot and coal had to be scrubbed from a rail tunnel under the Royal Docks, near London City airport, that hasn't been used since December 2006.

The Connaught Tunnel, a 500-metre tunnel originally opened in 1878 when steams trains used the tracks, is now stronger, wider, and deeper.

Crossrail/Business Insider

Two of Crossrail's eight mega tunnelling machines, Elizabeth and Jessica, were used to break through one of Europe's largest mined caverns.

Elizabeth barrelled through Stepney Green Cavern last November and Jessica followed in February this year. The Stepney Green cavern is 50 metres long and nearly 17 metres high.